Groundwater Research Articles

Spatial Analysis and Mapping of Ground Water Quality in Tiruvallur District

Spatial Analysis and Mapping of Ground Water Quality in Tiruvallur District

Interpretation of subsurface layers using the Wenner configuration geoelectric method and geochemical tests: Case study at Muara Fajar landfill – Rumbai, Pekanbaru

The need for water daily is a big problem for people living around Muara Fajar landfill – Rumbai, Pekanbaru. This study aims to identify the depth of subsurface structures around the Muara Fajar landfill area using the Wenner configuration dielectric method and determine the water quality in the community wells around the landfill site. The data obtained in the acquisition process are used to calculate the apparent resistivity value at each measurement point and analyzed quantitatively and qualitatively. Then proceed with the inversion process using the progress program so that obtained resistivity value and layer thickness at each point of measurement. The results of measurement in track-1 get a range of resistivity values ranging from 62.9 – 171 ohm-meters and track-2 from 32.4 – 70.6 ohm-meters. Underground water taken is residents' well water in the research area as many as 5 sample points using GPS. This underground water sample will be tested with parameters such as pH, TDS, BOD, COD, NH3, and turbidity. Underground water cannot be consumed from the results of the water quality test with the parameters mentioned at the beginning if referring to the Regulation of the Minister of Health of the Republic of Indonesia because the pH obtained in all underground water samples is < 6.5 or acidic, the value of the BOD, COD, NH3, and turbidity parameters, the values are by the quality standard.

Scientific-Practical Enhancement Principles for the Long-Term Stability of Cultural Heritage Objects through a Multi-Component Underground Space Analysis

This article presents approaches for enhancing engineering-geological and geotechnical research for the restoration and reconstruction projects of cultural heritage objects in St. Petersburg’s historical center. According to the Venice Charter, an interdisciplinary approach is recommended for developing a preservation program for cultural heritage objects. The authors consider the underground space as a multi-component system, where soils are a host medium for underground water with specific composition, complex physicochemical and biochemical conditions, the presence and vigorous activity of microorganisms, gases of various origins, and underground bearing and enclosing structures. The last of these components is crucial for the long-term stability of historical and cultural objects, as they interact in complex with water-saturated soils and microorganisms. This approach is not to be found in Russian cultural heritage preservation regulations. In engineering-geological and geotechnical research, multi-component underground space should be studied at the regional, local, and object levels. Assessing redox conditions in the underground environment is crucial for understanding the state of its components. Moreover, this can trigger hazardous processes such as changes in the stress–strain state and unconsolidation of the soil layer due to the generation of low-solubility gases and biocorrosion of ancient and modern building materials, causing premature destruction. Recommendations are provided for carrying out engineering-geological and geotechnical research based on cultural heritage objects, considering the multi-component underground space and features of its geoenvironmental state due to the long-term contamination and transformation of its components.

Transport Pathways of Nitrate in Stormwater Runoff Inferred from High-Frequency Sampling and Stable Water Isotopes.

Storm events can mobilize nitrogen species from landscapes into streams, exacerbating eutrophication and threatening aquatic ecosystems as well as human health. However, the transport pathways and storm responses of different nitrogen forms remain elusive. We used high-frequency chemical and isotopic sampling to partition sources of stormwater runoff and determine transport pathways of multiple nitrogen forms in an agricultural catchment. Bayesian mixing modeling reveals shallow subsurface water as the dominant source of stormwater runoff, contributing 74% of the water flux and 72, 71, and 79% of total nitrogen (TN), total dissolved nitrogen (TDN), and nitrate (NO3-N), respectively. Groundwater, by contrast, contributed 11% of stormwater runoff and 21, 22, and 17% of TN, TDN, and NO3-N, respectively. The remaining 14% of stormwater runoff can be attributed to rainwater, which contains much less TN, TDN, and NO3-N. Surprisingly, during storm events, the dominant nitrogen form was NO3-N rather than dissolved organic nitrogen. Antecedent conditions and runoff characteristics have an important influence on nitrogen loads during storm events. Our results provide insight into hydrological mechanisms driving nitrogen transport during storm events and may help in developing catchment management practices for reducing nitrogen pollution in aquatic ecosystems.

Seepage monitoring and leaks detection along an earth dam with a multi-sensor thermal-active system

Thermal investigation using linear sensors installed in the ground is currently one of the most effective methods for analyzing seepage processes in the bodies of earth dams or dikes and their subsoil, including leaks detection. However, linear, fiber-optic temperature sensors present several limitations when applied to existing structures, including installation difficulties and substantial costs. To enhance the applicability of the thermal method for studying subsurface water flow, a novel Multi-Point Thermal-Active Monitoring method has been devised. The approach consists of installing, through hammering, thermal-active sensors side-by-side in the ground, at the same depth in a single line thereby achieving quasi-continuous measurements along the structure. Small openings from sensor installation are secured with bentonite and do not pose a threat to the structure. Each sensor is equipped with a micro-heater, which enables the use of the thermo-active method to determine in-situ seepage velocity. This article describes this method and its initial application in 2014 on one of the Polish earth dams. This application enabled the detection of two leakage zones and the monitoring of their flow velocities, leading to the successful validation of the described technology.

Rapid Determination of 12 Classes of Per- and Polyfluoroalkyl Substances in Water Samples from Environmental Forensic Cases.

The widespread use of per- and polyfluoroalkyl substances (PFASs) with different physico-chemical properties poses a great threat to the environment and human health. Simultaneous detection of different classes of PFASs is a difficult task, especially for rapid analysis of polluted water samples in environmental forensic cases. In this study, a simple sample preparation ultrahigh-performance liquid chromatography coupled with quadrupole Orbitrap high-resolution mass spectrometry was established for the detection of PFASs in a wide range of water matrices. By optimizing the conditions of pretreatment and the parameters of the instrument, the developed method provided good linearity of calibration standards (R2 > 0.99), and demonstrated excellent MLOQ (0.008-1.2 µg/L), with spiked recoveries ranging from 57.7% to 151% for 47 targets in surface water samples, and from 45.7 to 165% for 46 targets in ground and waste water samples, respectively. This method required an injection volume of 3 µL and an analysis time of only 18 min per sample. The validation method was successfully applied to the analysis of 20 environmental water samples, in which 15 target substances with different concentrations were detected, with total concentrations of 0.082 to 262.455 μg/L. The method is simple and exclusive, and can rapidly confirm the occurrence of PFASs in different water samples, providing a convenient and fast high-throughput analysis, which is especially suitable for the application in the environmental forensic investigation of PFASs pollution.

Optimal groundwater depth and irrigation amount can mitigate secondary salinization in water-saving irrigated areas in arid regions

Secondary salinization poses a significant threat to the sustainable development of water-saving irrigation districts. This study aims to explore the spatial and temporal variations in soil salinity and the factors influencing these changes in water-saving irrigation areas in the inland arid regions of Northwest China. The Manas River Irrigation District was selected as the study area. A grid measuring 10 km × 14 km grid was designed to determine the latitude and longitude coordinates of the grid centers, resulting in 66 sample points. Soil samples were collected from these points in 2013, 2014, 2020, and 2021 from the 0100 cm layer to obtain salinity data. Based on existing research and practical conditions in water-saving irrigation areas, 11 factors influencing soil salinity changes were identified, including irrigation area and irrigation amount. Classical statistical methods and interpretable machine learning techniques were employed to analyze the distribution characteristics of soil salinity and the influencing factors. This analysis proposes effective solutions to mitigate potential secondary salinization in irrigation areas. The results revealed that soil salinity in the irrigation area belonged to moderate variation (Cv = 46.74 %51.80 %). The horizontal direction of the irrigation area shows higher salt content in the upstream and downstream areas, and a gradual decrease in variability with increasing depth characterizes the vertical direction. From 2013–2021, soil salinization in the irrigation area gradually decreased. In 2013 and 2014, the area was predominantly covered by mild saline-alkali soil, accounting for 75.1 % and 76.6 % of the total area, respectively. However, in 2020 and 2021, non-saline soils became dominant, covering 60.9 % and 66.5 % of the total irrigation area, respectively. In order of importance, the factors affecting the spatial and temporal evolution of soil salinity are groundwater depth, annual water surface evaporation, water-saving irrigation area, underground water diversion amount, mineralization of groundwater, irrigation amount, surface water diversion amount, and annual rainfall. In the oasis irrigation area, maintaining a groundwater depth of 4.06.0 m and an irrigation amount of 55006000 m3 ha−1 can alleviate the problem of secondary salinization that may result from large-scale development of water-saving irrigation. The findings of this study provide a basis for the prevention and control of soil salinization in water-saving irrigation areas and the development and management of saline land in oasis areas.

The Potential of Big Data and Machine Learning for Ground Water Quality Assessment and Prediction

The Potential of Big Data and Machine Learning for Ground Water Quality Assessment and Prediction

Mineralization and stabilization of toxic Pb2+ ions using CMC loaded S/P co-doped biochar composite

Creating more stable chemical precipitates containing lead using biochar composite represents a significant and promising strategy for the treatment of lead contamination. Biochar, a porous and carbonaceous material, was fabricated by pyrolyzing plant biomasses (i.e., soybean straw) under anoxic conditions. In this research, a high capacity of adsorbent called carboxymethyl cellulose-loaded sulfur-phosphorus co-doped biochar composite was prepared, and the optimal lead adsorption parameters and mechanism were also investigated. The experimental results showed that CMC@SP2BC exhibited excellent Pb2+ removal capacity, reaching 829.3 mg/g maximum adsorption under optimum conditions (dosage 0.5 g/L, temperature 308 K, initial pH 5, initial lead concentration 2000 mg/L), which was in agreement with the Langmuir and second-order kinetic models. Moreover, the sequential extraction results indicated that the predominant passivation mechanism for Pb was chemical precipitation, followed by ion exchange, complexation, and physical adsorption. In addition, structural characterization revealed that the passivated lead was mainly in the form of minerals such as PbSO4, Pb3(PO4)2, Pb5(PO4)3OH, and Pb5(PO4)3Cl, which was also further confirmed by PHREEQC model simulation at different pH value and Pb2+ concentrations. Finally, Pb2+ was effectively removed from actual ground water by CMC@SP2BC to achieve Class I and Class II ground water standard. The current work offers an efficient solution for immobilizing Pb2+, which has enormous promise for stabilizing heavy metals.

DESIGNING A GEOMETRY OF LOWWALL SLOPE IN COAL MINING USING THE LIMIT-EQUILIBRIUM METHOD AT THE WORKING AREA OF PT. PETROSEA TBK, TARAKAN BASIN, NORTH KALIMANTAN, INDONESIA

Mining, which involves extracting minerals and utilizing natural resources, requires careful planning to ensure feasibility and safety. A critical aspect of open pit mine design is slope stability, influenced by geological characteristics, slope topography, and groundwater conditions. Slope stability analysis, using methods such as the Limit Equilibrium Method (LEM), which has been popular for decades for its convenience, evaluates the potential for slope failure and provides geometric slope design recommendations to reduce risk, improve operational efficiency, and ensure environmental sustainability. The research was conducted at PT Petrosea Tbk, with the mine site in Sebakis Village, Sebuku Subdistrict, Nunukan Regency, North Kalimantan, PT X region. The research object is a lowwall slope that requires stability analysis to prevent landslides. The slope safety criteria are based on the Minister of Energy and Mineral Resources Decree No. 1827 K/30/MEM/2018 guidelines, specifically 1.1. To perform the analysis, laboratory test data is required, including rock physical property tests and rock shear strength tests to obtain material property values. This data was then analysed using Rocscience Slide2 software by comparing three methods: Bishop, Janbu, and Morgenstern-Price. The analysis was conducted based on the actual conditions of each slope cut geometry. If the obtained safety factor does not meet the criteria of the Minister of Energy and Mineral Resources Decree No. 1827 K/30/MEM/2018, then designing a geometry of lowwall slope is required. The geometric slope design used on the lowwall slope includes creating benches to flatten the slope level, and installing drain holes to decrease the ground water level.

Climate change induced salinization and quality deterioration of groundwater resources in Pakistan; Current scenario and future prospects

Climate change has triggered various catastrophic events including groundwater salinization resulted in quality deterioration worldwide leading to the environmental degradation and posed threat to natural ecosystems. Pakistan is among the countries severely affected by the climate change. Most of the Pakistani depends on groundwater resources for drinking and irrigation purposes but no clear policy exists regarding judicious extraction and usage of groundwater. Over extraction and exploitation of groundwater along with climate change events have deteriorated the quality of groundwater in Pakistan and most of the part is salinized and has excess of soluble salts and other chemical, physical and biological contaminants. This paper reviews the impacts of climate change on salinization and groundwater quality and possible remedies and solution for this problem especially with the perspective of Pakistan. It is the need of the hour of the time to introduce climate smart agricultural practices at farmer level to stop overexploitation of natural resources and to reduce the agriculture share to climate change. Policies should be developed and existing policies should be strictly implemented for the judicious use of surface water and ground water resources to avoid the risks of water scarcity in near future.

Decrease due to pollution in the rhizosphere microbial diversity can be amended by supplementation from adapted plants of another species

Manipulating the rhizosphere microbiome to enhance plant stress tolerance is an environmentally friendly technology and a renewable resource to restore degraded environments. Here we suggest a sustainable bioremediation strategy on the example of Stebnyk mine tailings storage. We consider Salicornia europaea rhizosphere community, and the ability of the phytoremediation plant Salix viminalis to recruit its beneficial microbiome to mediate the pollution stress at the Stebnyk mine tailings storage. The tailings contain large amounts of brine salts and heavy metals that contaminate the ground water and surrounding areas, changing soil biogeochemistry and causing increased erosion. The species richness of the endophytic bacterial community of S. viminalis roots was assessed based on observed OTUs, Shannon-InvSimpson, and evenness index. Our results obtained using the plant-based enrichment strategy show that biodiversity was decreased across the contamination zones and that S. europaea supplementation significantly increased the species richness. Our results also indicate that the number of dominating bacteria was not changed across zones in both S. europaea-treated and untreated bacterial populations, and that the decrease in richness was mainly caused by the low abundant bacterial OTUs. The importance of selecting the bioremediation strains that are likely to harbor a reservoir of genetic traits that aid in bioremediation function from the target environment is discussed

Experimental and finite element assessment of stabilizing configurations for underground heritage sites

Heritage sites in Alexandria, Egypt, are some of the UNESCO world heritage sites at high risk from geo-environmental hazards, in particular caused by sea level rise and heavy rain due to the climate change. Recently, safeguarding UNESCO world subterranean and built heritage draws more attention. After recent environmental catastrophies in Alexandria, sustainable conservation materials and stabilizing configurations of underground monumental structures has also become urgent and highly demanded. Based on typical damage due to the heavy weathering caused by the ground water table and salt, this paper offers a guide for engineers and conservators, where rock structures consolidation and stabilizing configurations to protect these structures in the static state and against strong seismic events is presented. In this paper, typical geotechnical problems and damage to the Catacombs of of Kom El-Shoqafa are presented first, followed by an experimental evaluation methodology that includes spectroscopic and morphological characterization in addition to the mechanical testing of untreated and treated rock samples with synthetic organosilicone and acrylic compounds. The effectiveness of the new silica-based consolidants was evaluated in terms of the amount of solid adsorbed, mechanical properties (e.g., surface hardness, ultrasonic velocity, modulus of elasticity and modulus of compressive strength), and resistance to salt crystallization. The treated groups showed better mechanical strength than the control group. The ability of the treated samples to resist climate change negative impact was also greatly improved. According to laboratory tests, new silica-based hardeners and hydrophobic materials have great potential for strengthening weathered Calcarenitic rock structures. It was observed that the rock samples containing the modified binder (MTMOS + Wacher BS 15) reach higher mechanical strength parameters. After the experimental study (testing procedures), FEM analysis was performed using PLAXIS 2D code to validate the silica-based consolidants and verify their efficiency in improving the response of rock structures in static and seismic states against strong earthquake events. The results of this work confirm the high potential of low-cost injection techniques and stabilizing configurations (pre- stressed anchors and concrete friction piles) technology, confirming the possibility of achieving significant improvement in the geotechnical properties of Calcarenitic rock structures and enhancing the seismic performance of underground archaeological structures using low-cost injection technology that is easy to manufacture.

Socio-economic Impact of Reducing Water Availability of Springs in Kandi Village, Devprayag, Uttarakhand: A People Perception Approach

Water is necessary for sustainable development, which includes safeguarding the environment and the reduction in hunger and poverty. Demand is rising quickly, which is posing issues for many countries due to population growth and economic expansion. The goal of the current study is to examine the state of spring and water resources in Kandi Village, Devprayag, Uttarakhand, India, and how they affect farmers’ agricultural productivity from a socioeconomic standpoint. The key data used in the study were gathered from farmers using questionnaires. Using a stratified random sampling technique, a sample of 100 farmers was chosen for the data collection. The conclusion of the study is that there is currently very little spring, and ground water available. It has been discovered that spring is sparse to fulfil the need of annual irrigation requirements for economic purposes like farming. Lack of springs resulted in a reduction in the amount of land used for farming, a decrease in farmer revenue, livestock losses, etc. According to the findings, some ways to lessen the strain on the water resources available to farmers include building new dams, rejuvenating springs, teaching them how to use highly efficient irrigation systems, and educating them about modern production techniques.

Implementasi Sistem Pertanian Organik di Desa Karangrejo, Kecamatan Gumukmas, Kabupaten Jember

The Mulyo Farmer Group of Karangrejo village are the fostered villages of the University of Jember and have long been food producers, especially rice and corn, with the potential to become one of the providers of organic products according to SNI 6729:2016. Therefore it is essential to evaluate the implementation of gab against the standard requirements of organic farming systems. Some of the activities carried out are Evaluation and increasing understanding of the application of organic farming systems by continuing the practice of making biochar from agricultural waste for long-term organic fertilizer base materials; Focus Group Discussion and ongoing assistance by the Soil Biodiversity and Fertility Research Group UNEJ. The results of the activities show that the community and village officials are thrilled and open to several activities to be carried out. The results of the initial evaluation using the checklist for fulfilling the requirements of SNI 6729:2016 are based on eight variables related to fresh plants and plant products, indicating that there is no program yet to meet the needs of the organic farming system of SNI 6729:2016 or it has not yet been fulfilled. Even though it has not been fulfilled, the potential for implementing it remains open if based on its main potential, namely organic fertilizer sources and water sources (lowlands with relatively shallow groundwater tables). The existence of many livestock and agricultural waste (which is not harvested) available throughout the year can be used as a source of organic fertilizer in maintaining soil fertility or health.

Assimilating multivariate remote sensing data into a fully coupled subsurface-land surface hydrological model

Hydrological models play a crucial role in tracking and predicting terrestrial water storage, yet they face challenges due to uncertainties and inaccuracies caused by various factors such as meteorological processes and data limitations. To refine these models, data assimilation has emerged as a valuable tool, utilizing a new source of data to update model states while considering associated uncertainties, thereby enhancing our comprehension and predictive capabilities in hydrological processes. In this context, satellite data are receiving increasing attention because they can cover large areas and are useful in detecting spatial and temporal variability of water.In most existing studies related to satellite data assimilation in hydrological models, one source satellite data is used in the analysis. This study focuses on improving subsurface water storage model accuracy by assimilating data from different satellite sources. In particular, we used data from the Soil Moisture and Ocean Salinity (SMOS) satellite and terrestrial water storage data from the Gravity Recovery and Climate Experiment (GRACE). The data are assimilated into a fully coupled subsurface-surface hydrological model, developed with ParFlow-CLM (PARallel FLOW- Community Land Model). The investigation is conducted in Iran. Employing an Ensemble Kalman Filter, three assimilation scenarios are explored: (i) GRACE, (ii) SMOS, and (iii) the combined assimilation of both GRACE and SMOS data (joint). Findings are validated against the Soil Moisture Active Passive (SMAP) and in-situ groundwater data by using a novel probabilistic reliability framework, demonstrating the advantages of joint data assimilation.The study highlights the influence of assimilated remote sensing data type on the effectiveness of data assimilation. Assimilating GRACE data enhances groundwater level estimations. However, SMOS data positively impacts topsoil moisture estimations, but adversely affects groundwater level estimates. Importantly, the assimilation of both GRACE and SMOS data through multivariate (joint) data assimilation significantly improves accuracy for both soil moisture estimation and groundwater level estimation.

Dietary salt concentrations influence growth, nutrient utilization, and fatty acid profiles of turbot (Scophthalmus maximus) reared in brackish water.

Expansion of economically viable turbot (Scophthalmus maximus) aquaculture depends on access to brackish-cold ground water sources in various parts of the world. Since brackish water sources can adversely affect the physiology and zoo technical performance of fish due to the burden of osmoregulation, dietary salt inclusion can alleviate the negative impacts of low-saline waters in several aquaculture species. This study investigated the effects of increasing dietary salt levels on the growth, feed utilization, body composition, and tissue fatty acid composition of juvenile turbot (initial live weight 120.3 ± 0.03g/fish). Fish were fed five experimental diets supplemented with varying levels of sodium chloride (1.8-6.4%) or a control diet without salt. Each diet was tested in triplicate tanks for 9weeks. Results showed that increasing dietary salt intake negatively impacted turbot performance, with significant reductions in weight gain, specific growth rate, and feed conversion ratio. Dry matter and ash content in the whole body and filet increased quadratically with increasing salt levels, whereas gill moisture and protein content decreased linearly. Furthermore, the nitrogen, lipid, and energy utilization efficiencies decreased with their respective intake and gain levels. Dietary salt significantly influenced the fatty acid profiles of gill, liver, and filet tissues. In the gill, monounsaturated fatty acids (16:1n-7, ΣMUFA) and n-6 PUFA (20:2n-6) increased, whereas EPA and DHA decreased. Liver ΣSFA (16:0, 18:0) increased, and n-3 PUFA (18:3n-3, 20:5n-3) decreased with increasing dietary salt. Filet saturated fatty acids (14:0, 15:0, 17:0) and n-6 PUFA (20:2n-6, 20:4n-6) increased, while n-3 PUFA (18:3n-3, EPA) decreased with dietary salt. DHA levels in filets showed a quadratic increase. Overall, this study shows that increasing dietary salt negatively impacts turbot growth, feed utilization, and tissue fatty acid composition in brackish water, highlighting the need for further studies on salinity management strategies for turbot aquaculture.

Controlled release formulations of organophosphorus pesticides based on ecofriendly novel and conventional matrices for agro-environmental sustainability

Controlled release formulations (CRFs) of the organophosphorus pesticides diazinon and dichlorvos were prepared from a novel cow dung ash (CDA) matrix and the more conventional starch (STA) matrix. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the CRFs. FTIR and XRD spectral data provide evidence for pesticide-matrix interactions fundamental to observed matrix surface binding and pesticide release behaviour in water and soil environments. Properties evaluation of the CRFs reveal similar magnitudes of loading capacity and encapsulation efficiency of CDA- and STA-based CRFs of both pesticides, while the order CDA > STA prevails in matrix porosity and swelling ability. Technical grade (TG) and the CRF-encapsulated pesticides exhibit “burst” release profiles in water; pesticide quantities released at similar lengths of time follow the order TG >> STA-CRF > CDA-CRF, thus revealing the capacity of the CRFs to constrain the active ingredients from free mobility, with CDA-CRF being the more slightly efficacious. The Korsmeyer-Peppas equation reasonably models pesticide release from both CRFs into water, giving n values consistent with both water diffusion into the matrix and matrix relaxation as kinetically important in both matrices. Soil column experiments demonstrate the potential of the CFRs to mitigate ground water pollution. Overall, the results show that CDA- and STA-based CRFs of both pesticides have roughly the same potency for pesticide controlled release and ground water pollution mitigation. Deployment of these CFRs can contribute to the drive for agro-environmental sustainability, while the use of CDA, a waste material, as a matrix in controlled pesticide delivery would resonate with sustainable bioresource utilization.

(Invited) Efficient Recycling of Dilute Nitrate to Ammonia Using Cu-Based Electrocatalyst

The use of nitrogen fertilizers has contributed significantly to the growth of agricultural production, but the nitrogen use efficiency is typically lower than 40%, so most of the nitrogen readily leaches into ground water, rivers, and lakes, causing an increase of nitrate (NO3 −) concentration and severe environmental problems. Electrochemical reduction of nitrate has emerged as a promising route for the recycling of nitrate from wastewater and sustainable production of ammonia when powered by renewable electricity. Here I present our recent studies of the intrinsic activity and selectivity of Cu for nitrate electroreduction, as well as a rational design of Cu-based catalysts for single-pass conversion of nitrate to ammonia. Using polycrystalline Cu foils for benchmarking, we elucidated the impact of often overlooked factors on nitrate reduction, including Cu facet exposure, nitrate concentration, and electrode surface area. We find that an electropolished Cu foil exhibits a higher activity and selectivity for nitrate reduction to ammonia than a wet-etched Cu foil, benefiting from a greater exposure of Cu(100) facets that are more favorable for the reaction. The NH3 selectivity shows no apparent dependence on the nitrate concentration, but it increases monotonically with Cu electrode area, which is attributed to a promoted conversion of intermediately produced NO2 − to NH3 on a larger electrode. Based on the understandings, we further developed a Cu/Co-based tandem electrocatalyst, which achieved nearly 100% single-pass conversion of dilute nitrate (5−50 mM) to NH3 at a low overpotential using a flow cell.

Metal-Organic Framework-Based Materials for Heavy Metal Sensing in Aqueous Media

Industrial development leads to an increasing amount of pollutants including heavy metal ions in surface and subsurface waters. For instance, wastewater from battery manufacturing, paint manufacturing or metal plating, contain heavy metals in high concentrations. The heavy metals are typically non-biodegradable and not-easy to excrete. Their presence within the organisms causes damage and failure of different organs. Consequently, the permissible concentrations of heavy metal ions in drinking water set by the World Health Organization are on a ppb level.In this work, electrode materials based on metal-organic frameworks (MOFs) are prepared and studied for sensing of heavy metals in aqueous media. These involved MOFs in their pristine form, composites of pristine MOFs and conducting polymer polyaniline as well as their carbonized derivatives. Cadmium and lead ions were used as model pollutants. Thorough physico-chemical characterization of the prepared materials was done using scanning electron microscopy, Raman spectroscopy, and dynamic light scattering. Electroanalytical performance was scrutinized using anodic stripping voltammetry and correlated with materials’ structural, morphology and textural properties. Limits of detection and sensitivity were determined upon optimization of the experimental conditions to identify the best material. Moreover, materials proved to be suitable for two heavy metal ions sensing in real river samples. Acknowledgments This work was supported by the Science Fund of the Republic of Serbia, grant number 7750219, Advanced Conducting Polymer-Based Materials for Electrochemical Energy Conversion and Storage, Sensors and Environmental Protection-AdConPolyMat (IDEAS programme).